According to one conventional method of acquiring fingerprint data, an ink impression of a fingerprint is printed on paper for subsequent scanning into a digital computer. According to this method, the finger is stained with ink each time the fingerprint data is entered. Any uneven coating or blurring of the ink hinders the input operation, as does any lateral motion or shear of the inked finger when applied to the paper. To ensure that enough information is obtained during data input or enrollment, the finger is typically "rolled" across the paper to transfer a greater portion of the surface of the person's finger thereto. While the rolling step increases the overall amount of data acquired, the increased risk of finger shear undermines the integrity of the acquired data. Further, geometric or electronic distortion may be introduced during the process of scanning the data into the digital computer.
According to more modern methods, fingerprints are obtained by reflecting or scattering an image of the finger surface onto an image sensor, such as a charge coupled device. Devices that perform this function are described in, for example, U.S. Pat. No. 4,924,085 to Kato et al., U.S. Pat. No. 5,088,817 to Igaki et al., and U.S. Pat. No. 5,067,162 to Driscoll, Jr., et al., the disclosures of which are hereby incorporated by reference as though set forth in their entirety herein. In each of these systems, a light source is irradiated at an angle onto the ridge and groove portions of a fingerprint which has been pressed against a light conducting plate. Depending upon the particular orientation of the light source with respect to the light conducting plate, and the location of the image sensing device, either the reflected or the scattered light from the fingerprint is transferred. The image sensor captures the transferred light so that the captured fingerprint data can be stored. These fingerprint readers have comprised relatively large optical systems having numerous optical components or, in an attempt to simplify the optical system, for example, as in the U.S. Pat. No. 4,924,085, have sacrificed resolution and geometric fidelity.
What has been needed and has heretofore not been fulfilled in the art, is an uneven surface image transfer system that provides an unadulterated signal of high resolution at an image sensing device that is remote of the image transfer platen in a low cost system. Also needed is an apparatus that provides an uneven surface image transfer system with the aforementioned advantages, in a unitary structure. Of further benefit to the art, would be such a system that further allows the transfer of images such as bar code data. The present invention satisfies these and other needs in an uneven surface image transfer apparatus.